Aglass is 4/7 full . then 70cm3 of orange juice is poured in . the glass is now 2/4 full. what is the total volume of the glss

Let 
x> total volume of a glass

we know that
(4/7)x-70=(2/4)x> (4/7)x-70=(1/2)x> 2*(4/7)x-2*70=x
(8/7)x-140=x

multiplied by 7 the expresion
7*(8/7)x-7*140=7*x> 8x-980=7x> x=980 cm³

the answer is 
the total volume of the glass is 980 cm³

20000 as first it increases by 2500 then by 5000 so next it will increase by 10000